1. Field of Invention
The invention relates to an automatic transmission mounted in a vehicle, and more particularly to a hydraulic control apparatus for controlling friction elements in such a transmission.
2. Description of Related Art
In the automatic transmissions of vehicles in recent times, a structure is employed wherein in the hydraulic pressure circuit that controls clutches and brakes (in this specification, these shall be referred to as xe2x80x9cfriction elementsxe2x80x9d) used to achieve each speed, exclusive control means (combining a linear solenoid valve, a duty solenoid valve or a linear solenoid valve with a regulating valve) are provided for each hydraulic servo of each friction element, and these are each controlled independently in order to improve control. The control means in such a hydraulic pressure circuit is supposed to secure a certain level of running ability of the vehicle by accomplishing hydraulic output to the hydraulic servo even during signal failures, and is supposed to be a normally open valve for accomplishing hydraulic output during times of no signal. Consequently when all of the control means simultaneously experience signal failures or sticking failures, an interlock condition arises wherein friction elements that originally were not to engage simultaneously engage. In order to prevent such a condition, technology for avoiding interlocking even in the event of the control means supplying hydraulic pressure because of an electrical failure or sticking of the valves or the like (hereinafter, collectively referred to as xe2x80x9cfailuresxe2x80x9d) when the vehicle is moving forward has been disclosed in Japan Patent 53-8028.
In the aforementioned art, it is possible to prevent interlocking by providing an interlock valve (134, 136, 138 and 140 in FIG. 2 of the aforementioned disclosure) for providing hydraulic pressure to each friction element as a signal pressure during failures. Furthermore, the interlock valve is a valve used to cut off all hydraulic pressure to friction elements disengaged at preset speeds, and hence when a failure occurs at a preset speed, that speed is fixed. As a result, it is possible to resolve the problems of insufficient drive force or over-revving by maintaining a constant speed when failures occur.
However, the aforementioned art is such that each speed is achieved by engaging a friction element (54) that is always engaged with exclusive friction elements (48, 52, 56, 58) engaged in each speed, and consequently, the structure is such that only hydraulic pressure to the exclusive friction elements is applied in the aforementioned interlocking. Accordingly, in a gear train where there are no exclusive friction elements in each speed, the problem arises that this technology cannot be adapted.
Hence, it is the general objective of the invention to provide a hydraulic control apparatus that can maintain the achieved speed in the event of failures in an automatic transmission comprising a plurality of speeds using the same friction elements in achieving differing speeds, that is to say in an automatic transmission in which exclusive friction elements do not exist for each speed.
In order to achieve the above-described objective, in a first aspect a hydraulic control apparatus for an automatic transmission, of the type of hydraulic control apparatus provided with a plurality of friction elements and hydraulic servos for operating such, and wherein a plurality of speeds can be achieved by engaging at least two friction elements at a time out of the plurality of friction elements; and provided with a switching means for cutting off hydraulic control to the friction elements other than the friction elements engaged in order to achieve each speed within the plurality of speeds; wherein the plurality of speeds includes a third speed which, from among the friction elements, engages at least the first and third friction element and disengages the second friction element, a fourth speed which engages the first and second friction elements and disengages the third friction element, and a fifth speed which engages the second and third friction elements and disengages the first friction element; and said switching means includes a first switching valve which cuts off hydraulic control to the first friction element by applying, as a signal pressure, hydraulic pressure to the third friction element engaged in at least the third and fifth speeds and the second friction element engaged in the fifth speed, and a second switching valve that cuts off hydraulic control to the third friction element by applying, as a signal pressure, hydraulic pressure to the first friction element engaged in the third and fourth speeds and the second friction element engaged in the fourth speed.
In the above-described structure, it is effective as a second aspect for the structure to be further equipped with a plurality of control means capable of adjusting the hydraulic pressure to each hydraulic servo that operate the plurality of friction elements; wherein the hydraulic pressure from the plurality of control means is provided to each of the hydraulic servos.
Furthermore, in the above-described structure, a third aspect is effective for the structure to be provided with a hydraulic pressure source and first and second oil paths connecting the hydraulic pressure source with the hydraulic servos of the first and third friction elements, such that from among the plurality of control means, the first and second control means are positioned on these first and second oil paths; and the first and second switching valves are respectively positioned on the first and second oil paths, and cut off the supply of hydraulic pressure from the hydraulic pressure source to the other hydraulic servos by a hydraulic pressure being applied on the downstream side of the control means regulating the hydraulic pressure to the engaged friction elements.
In addition, in the above-described structure, a fourth aspect is effective in the structure for switching means to be such that the hydraulic pressure other than the pressure on the other friction elements, to which the hydraulic pressure supply is cut off, is applied as a signal pressure.
In addition, a fifth aspect is the above-mentioned plurality of friction elements may further include a fourth friction element, with the fourth friction element disengaged in the third, fourth and fifth speeds.
In addition, a structure may also be employed as a sixth aspect wherein the plurality of speeds further includes a second speed that engages the first and fourth friction elements and disengages the second and third friction elements, and a sixth speed that engages the second and fourth friction elements and disengages the first and third friction elements; and the first switching valve cuts off the hydraulic pressure supply to the first friction element by applying, as a signal pressure, a hydraulic pressure to the fourth friction element that is engaged at least in the case of the second speed, and a hydraulic pressure on the second friction element engaged in the case of the sixth speed.
In addition, a structure may also be employed according to a seventh aspect wherein the switching means includes a third switching valve capable of cutting of the hydraulic pressure supply to the second friction element, and the third switching valve is operated by hydraulic pressure to a friction element that engages in speeds where the second friction element is disengaged.
Or, a structure may be employed according to an eighth aspect wherein the switching means includes a third switching valve capable of cutting off the hydraulic pressure supply to the second friction element, wherein the third switching valve is operated by hydraulic pressure other than the hydraulic pressure to a friction element that engages in speeds where the second friction element is disengaged.
In the above-mentioned case, as a ninth aspect it is effective for the hydraulic pressure other than the hydraulic pressure to be a friction element is a solenoid pressure output by electrical control.
In addition, a structure may be employed as a tenth aspect wherein the first switching valve capable of cutting off the hydraulic pressure supply to the first friction element has a first operating means that operates switching of the first switching valve.
In the above-mentioned case, it is effective to employ a structure as an eleventh aspect wherein the first operating means cuts off the hydraulic pressure supply to the first friction element by switching the first switching valve by means of hydraulic pressure to the friction elements engaged in fifth speed, in which the second and third friction elements are engaged and the first and fourth friction elements are disengaged, and friction elements engaged in sixth speed, in which the second and fourth friction elements are engaged and the first and third friction elements are disengaged.
In addition, a structure may be employed in a twelfth aspect wherein the switching means is composed of a first group of switching valves capable of cutting off the hydraulic pressure supply to the third friction element, and the first group of switching valves has a first group of operating means for operating the switching thereof.
In addition, a structure may also be employed in a thirteenth aspect wherein the first group of operating means cuts off the hydraulic pressure supply to the third friction element by switching the first group of switching valves by means of hydraulic pressure (C1 apply pressure and C2 apply pressure in fourth speed; C2 apply pressure along with B1 apply pressure and B1 solenoid pressure in sixth speed) to the friction elements engaged in fourth speed, in which the first and second friction elements are engaged and the third and fourth friction elements are disengaged, and friction elements engaged in sixth speed, in which the second and fourth friction elements are engaged and the first and third friction elements are disengaged.
In addition, a structure may also be used in a fourteenth aspect wherein the first group of switching valves comprises a first switching valve of the first group and second switching valves of the first group, and the first switching valve of the first group cuts off the hydraulic pressure supply to the third friction element through hydraulic pressure to the friction elements engaged in the fourth speed in which the first and second friction elements engage and the third and fourth friction elements disengage, and the second switching valves of the first group cut off the hydraulic pressure supply to the third friction element through hydraulic pressure to the friction elements engaged in the sixth speed in which the second and fourth friction elements engage and the first and third friction elements disengage.
In the above-described structure, a structure may also be used in a fifteenth aspect wherein the switching means includes a second group of switching valves capable of cutting off the hydraulic pressure supply to the fourth friction element, and is further provided with a second group of operating means for operating switching of the second group of switching valves.
In addition, a structure of a sixteenth aspect may be used wherein the second group of operating means cuts off the hydraulic pressure supply to the fourth friction element by switching the second group of switching valves through hydraulic pressure (C3 solenoid pressure in third speed, C1 apply pressure and C2 apply pressure in fourth speed, and C3 solenoid pressure in fifth speed) to the friction elements engaged in third speed in which the first and third friction elements engage and the second and fourth friction elements disengage, fourth speed in which the first and second friction elements engage and the third and fourth friction elements disengage, and fifth speed in which the second and third friction elements engage and the first and fourth friction elements disengage.
In addition, a structure of a seventeenth aspect may be used wherein the second group of switching valves comprises a first switching valve of the second group and second switching valves of the second group, and the first switching valve of the second group cuts off the hydraulic pressure supply to the fourth friction element by means of hydraulic pressure to the friction elements engaged in fourth speed in which the first and second friction elements engage and the third and fourth friction elements disengage, and the second switching valve of the second group cuts off the hydraulic pressure supply to the fourth friction element by switching the second group of switching valves by means of hydraulic pressure to the friction elements engaged in third speed in which the first and third friction elements engage and the second and fourth friction elements disengage, and fifth speed in which the second and third friction elements engage and the first and fourth friction elements disengage.
In addition, a structure may be used in an eighteenth aspect wherein the switching means includes a third switching valve capable of cutting off the supply of hydraulic pressure to the second friction element, and is further provided with a third operating means that operates switching of the third switching valve.
In addition, a structure may also be used in a nineteenth aspect wherein the third operating means cuts off the hydraulic pressure supply to the second friction element by switching the third switching valve by means of hydraulic pressure (C1 apply pressure and B1 apply pressure in second speed, and C1 apply pressure and C3 apply pressure in third speed) to the friction elements engaged in second speed in which the first and fourth friction elements engage and the second and third friction elements disengage, and third speed in which the first and third friction elements engage and the second and fourth friction elements disengage.
In addition, a structure may also be used in a twentieth aspect wherein the switching means includes a third switching valve capable of cutting off the supply of hydraulic pressure to the second friction element, and is further provided with a third operating means for operating switching of the third switching valve.
In addition, a structure may also be used in a twenty-first aspect wherein the third operating means is capable of cutting off the supply of hydraulic pressure to the second friction elements by means of hydraulic pressure unrelated to the hydraulic pressure to the friction elements engaged in speeds in which the second friction element disengages.
In addition, a structure of a twenty-second aspect may also be used wherein the second switching valve of the second group cuts off the supply of hydraulic pressure to the fourth friction element by means of hydraulic pressure to the third friction element.
In addition, a structure of a twenty-third aspect may also be used wherein the second switching valve of the first group cuts off the supply of hydraulic pressure to the third friction element by means of hydraulic pressure to the second friction element and fourth friction element.
In addition, a structure may also be used in a twenty-fourth aspect wherein the second switching valve of the first group cuts off the supply of hydraulic pressure to the third friction element by means of hydraulic pressure to the fourth friction element.
Next, the invention in a twenty-fifth aspect is of the type of hydraulic control apparatus provided with a plurality of friction elements and hydraulic servos for such, and wherein a plurality of speeds (first through sixth speeds) are achieved by appropriate operation of the plurality of friction elements, and at least one friction element out of the plurality of friction elements is engaged in two or more speeds; wherein a plurality of switching valves capable of cutting off the supply of hydraulic pressure to each of the hydraulic servos is provided between the hydraulic pressure source and each of the hydraulic servos that operate the plurality of friction elements; and operating means for operating switching of a specific switching valve out of the plurality of switching valves so that the supply of hydraulic pressure is cut off to the friction elements disengaged in a predetermined speed out of the plurality of speeds, are also provided.
In the above-mentioned structure, a structure may also be used in a twenty-sixth aspect wherein the plurality of friction elements includes at least first through fourth friction elements; the plurality of switching valves includes first through fourth switching valves that are positioned between the hydraulic pressure source and each hydraulic servo that operates the first through fourth friction elements, and that are capable of cutting off the supply of hydraulic pressure to the respective hydraulic servos; and the operating means includes first through fourth operating means that operate switching of the first through fourth switching valves so that the hydraulic pressure is cut off to the friction elements disengaged at a predetermined speed out of the plurality of speeds.
With the structure of the aforementioned first aspect, when in fourth speed the hydraulic pressure to the third friction element is cut off with the hydraulic pressure to the first friction element as a signal pressure, hydraulic pressure to the second friction element engaged in fourth speed is also applied as a signal pressure, and in addition, when in fifth speed the hydraulic pressure to the first friction element is cut off with the hydraulic pressure to the third friction element as a signal pressure, hydraulic pressure to the second friction element engaged in fifth speed is also applied as a signal pressure, and through this fourth or fifth speed is fixed even if a failure arises in that speed. In addition, third speed is also achieved with certainty.
Next, with the structure of the second aspect, it is possible to achieve the aforementioned efficacy even when a situation arises in which hydraulic pressure is output through failure of each control means.
Furthermore, with the structure of the third aspect, control linked to the second and third friction elements is established for the first friction element, and control linked to the first and second friction elements is established for the third friction element. As a result, fixation of the speed during failures is possible for third through fifth speeds.
Next, with the structure of the fourth aspect, the supply of hydraulic pressure to the hydraulic servos of the friction elements that are to maintain engagement is not cut off by the mutual action of the switching valves, and consequently it is not necessary to do processes such as adding separate signal pressure application circuits for self-maintenance.
In addition, with the structure of the fifth aspect, when there is a fourth friction element for achieving another speed that does not participate in achieving the third through fifth speeds, it is possible to achieve fixing of the third through fifth speeds during failures.
Furthermore, with the structure of the sixth aspect, when in sixth speed, that speed is fixed even if failures arise by applying hydraulic pressure to the second friction element and to the fourth friction element as signal pressures. In addition, it becomes possible to supply hydraulic pressure to the first friction element when in second speed, so that it is possible to achieve second speed with certainty.
Furthermore, with the structure of the seventh aspect, during failures in speeds where disengagement of the second friction element is to be maintained, the third switching valve acts through the hydraulic pressure of the engaged friction elements to prevent the supply of hydraulic pressure, and through this the disengagement status of the second friction element is maintained with certainty.
In addition, with the structure of the eighth aspect, during failures in speeds where disengagement of the second friction element is to be maintained, the third switching valve acts through hydraulic pressure other than of the engaged friction elements to prevent the supply of hydraulic pressure, and through this the disengagement status of the second friction element is maintained with certainty without regard to the speed that is achieved.
In particular, with the structure of the ninth aspect, in the aforementioned case, by setting up the third switching valve to cut off when solenoid pressure is not output, it is possible to achieve the disengagement status of the second friction element with certainty without regard to other friction elements during failures in speeds where disengagement of that element is to be maintained.
Next, with the structure of the tenth aspect, it is possible to operate the first friction element with the first operating means corresponding thereto.
In particular, with the structure of the eleventh aspect, it is possible to make the first friction element a friction element that disengages in fifth and sixth speeds.
Next, with the structure of the twelfth aspect, it is possible to operate the third friction element with the first group of operating means corresponding thereto.
In particular, with the structure of the thirteenth aspect, it is possible to make the third friction element a friction element that disengages in fourth and sixth speeds.
In particular, with the structure of the fourteenth aspect, for the third friction element, engagement in fourth speed is prevented by the action of the first switching valve of the first group, and engagement in sixth speed is prevented by the action of the second switching valve of the first group.
Next, with the structure of the fifteenth aspect, it is possible to operate the fourth friction element with the second group of operating means corresponding thereto.
In particular, with the structure of the sixteenth aspect, it is possible to make the fourth friction element a friction element that disengages in fourth and fifth speeds.
In particular, with the structure of the seventeenth aspect, for the fourth friction element, engagement in fourth speed is prevented by the action of the first switching valve of the second group, and engagement in fifth speed is prevented by the action of the second switching valve of the second group.
Next, with the structure of the eighteenth aspect, it is possible to operate the second friction element with the third operating means corresponding thereto.
In particular, with the structure of the nineteenth aspect, it is possible to make the second friction element a friction element that disengages in second and third speeds.
Next, with the structure of the twentieth aspect, for the second friction element, independent disengagement control is possible. Accordingly, by making the second friction element correspond to a friction element on the low speeds side with a low possibility of being in use during normal running of the vehicle, it is possible to prevent the circuit structure from becoming complex in order to fix a speed on the high speed side during failures.
In particular, with the structure of the twenty-first aspect, for the second friction element, independent disengagement control is possible without regard to the operation of other friction elements.
In particular, with the structure of the twenty-second aspect, during failures in speeds in which the third friction element is an engaged element, it is possible to prevent, with certainty, interlocking through tie-up of the fourth friction element.
In particular, with the structure of the twenty-third aspect, during failures in speeds in which the second friction element and the fourth friction element are engaged elements, it is possible to prevent, with certainty, interlocking through tie-up of the third friction element.
In particular, with the structure of the twenty-fourth aspect, during failures in speeds in which the fourth friction element is an engaged element, it is possible to prevent with certainty interlocking through tie-up of the third friction element.
Next, with the structure of the twenty-fifth aspect, it is possible to selectively disengage each friction element by placing a switching valve respectively in each hydraulic servo that operates each friction element and, thus, it is possible to obtain the efficacy of being able to fix each speed when a failure occurs in that speed.
In addition, with the structure of the twenty-sixth aspect, fixing during failure becomes possible for four speeds, and hence fixing of speeds corresponding to substantially all speeds during normal vehicle operation becomes possible.